/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | foam-extend: Open Source CFD
   \\    /   O peration     | Version:     4.1
    \\  /    A nd           | Web:         http://www.foam-extend.org
     \\/     M anipulation  | For copyright notice see file Copyright
-------------------------------------------------------------------------------
License
	This file is part of foam-extend.

	foam-extend is free software: you can redistribute it and/or modify it
	under the terms of the GNU General Public License as published by the
	Free Software Foundation, either version 3 of the License, or (at your
	option) any later version.

	foam-extend is distributed in the hope that it will be useful, but
	WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
	General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with foam-extend.  If not, see <http://www.gnu.org/licenses/>.

Description
	Algebraic Multigrid solver with run-time selection of coarsening and cycle

Author
	Klas Jareteg, 2013-04-15

\*---------------------------------------------------------------------------*/

#include "BlockAMGSolver.H"

// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

template<class Type>
Foam::BlockAMGSolver<Type>::BlockAMGSolver
(
	const word& fieldName,
	const BlockLduMatrix<Type>& matrix,
	const dictionary& dict
)
:
	BlockIterativeSolver<Type>
	(
		fieldName,
		matrix,
		dict
	),
	amg_
	(
		matrix,
		dict
	)
{}


// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

template<class Type>
typename Foam::BlockSolverPerformance<Type>
Foam::BlockAMGSolver<Type>::solve
(
	Field<Type>& x,
	const Field<Type>& b
)
{
	// Prepare solver performance
	BlockSolverPerformance<Type> solverPerf
	(
		typeName,
		this->fieldName()
	);

	Type norm = this->normFactor(x, b);

	// Calculate initial residual
	solverPerf.initialResidual() = cmptDivide(gSum(cmptMag(amg_.residual(x, b))),norm);
	solverPerf.finalResidual() = solverPerf.initialResidual();

	// Stop solver on divergence
	Type minResidual = solverPerf.initialResidual();
	scalar divergenceThreshold = 2;

	if (!this->stop(solverPerf))
	{
		do
		{
			amg_.cycle(x, b);

			  solverPerf.finalResidual() =
				  cmptDivide(gSum(cmptMag(amg_.residual(x, b))), norm);

			solverPerf.nIterations()++;

			// Divergence check
			if
			(
				cmptMax
				(
					solverPerf.finalResidual()
				  - divergenceThreshold*minResidual
				) > 0
			 && solverPerf.nIterations() > 5
			)
			{
				break;
			}

			minResidual = Foam::min(minResidual, solverPerf.finalResidual());

		} while (!this->stop(solverPerf));
	}

	return solverPerf;
}


// ************************************************************************* //
